Light Powers the World's Smallest Programmable Robot, at About 0.3 Millimeters Long

When you think of a robot, your go-to is probably WALL-E, C-3PO, or R2-D2. These hunks of bolts and metal paneling bear little in common with the microrobots that have become widely used across biology and medicine.

A pair of new studies, published in Science Robotics and the Proceedings of the National Academy of Sciences, details the latest advance in the field of medical microrobots: the creation of the world’s smallest programmable and autonomous robots. This robot is approximately 0.3 millimeters long, slightly smaller than the ridge of a fingerprint and barely visible without magnification.

Despite their tiny size, these robots can be preprogrammed and sense temperature and even tweak their movement in response. Researchers hope that robots could provide a method for monitoring the physiology of individual cells.

Marc Miskin, an engineering researcher at the University of Pennsylvania and senior author of both studies, said in a press release, "We've made autonomous robots 10,000 times smaller. That opens up an entirely new scale for programmable robots."

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Robots Moving Their Surroundings

Researchers have previously developed microrobots capable of drug delivery and in-body health monitoring, but have faced challenges. One of the most substantial of these roadblocks is the remote control of a machine smaller than a grain of sand within a body, where fluid flow creates strong drag.

Instead of trying to move the robot, Miskin’s project developed a way to move the machine’s surroundings. The robots generate a strong electrical field that exerts a force on ions in the surrounding liquid. These ions then nudge nearby water molecules, which push the robot forward. This propulsion system requires no moving parts, making the robots highly durable. They can swim around in liquid for months and can even be transported inside a pipette.

The robots are powered by tiny microcomputers developed by David Blaauw and Dennis Sylvester, engineers at the University of Michigan. Their processors run on just 75 nanowatts of power, around one hundred million times less than an LED lightbulb uses. The robot scavenges this power using mounted solar panels.

"We had to totally rethink the computer program instructions, condensing what conventionally would require many instructions for propulsion control into a single, special instruction to help us shrink the program's length to fit in the robot's tiny memory," Blaauw said in a press release.

Light pulses program the robot, so a group of machines could each respond to different commands.

Nature Inspires Tiny Robots

In the published papers, Miskin’s team tested the robot's ability to report temperature using on-board sensors. The machines were programmed to move toward areas of higher temperature and then report the exact value with precise micromovements detectable by the onlooking researchers. These movements could then be decoded to read the temperature.

Blaauw said this technique was inspired by the “waggle dance” that honeybees use to indicate nearby food sources to other bees. The robots could also report temperature as an indicator of cellular activity, meaning they could be used to monitor cell health.

"This is really just the first chapter," said Miskin. The team hopes that future robots could store more complex programs, sense more in their environment, and operate in more challenging conditions.

"We've shown that you can put a brain, a sensor, and a motor into something almost too small to see, and have it survive and work for months. Once you have that foundation, you can layer on all kinds of intelligence and functionality. It opens the door to a whole new future for robotics at the microscale,” Miskin concluded.

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Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

• This article references information from a study published in the journal Science Robotics: Microscopic robots that sense, think, act, and compute
• This article references information from a study published in the journal PNAS: Electrokinetic propulsion for electronically integrated microscopic robots